A conventional example of a display device that allows a viewer to see a real image of an object to be viewed formed in the air by using an optical plate is disclosed in, for example, Patent Document 1 listed below. This display device forms a real image of an object to be viewed in the air by having light from the object to be viewed reflected by an optical plate (dihedral corner reflector array) and directing the reflected light into the air on a side opposite to the side where the object to be viewed is located.
Normally, a midair image is formed at a position planar symmetric to an object to be viewed with respect to an optical plate. Hence, in a case of forming an image at a position far away from the optical plate in order to provide an image easy for a viewer to see, the object to be viewed needs to be placed far away from the optical plate, as a result of which the space on the object-to-be-viewed side of the optical plate becomes large. This problem is dealt with in Patent Document 1 by providing at least one reflective mirror in an optical path between an object to be viewed and an optical plate to thereby bent the optical path to reduce the space on the object-to-be-viewed side of the optical plate, and thereby a compact display device is achieved.
In Patent Document 2, for example, an optical image formation device is disclosed which has a light-controlling panel, a display unit, and a mirror member (first mirror member). The light-controlling panel is composed of first and second light-controlling members, which each have a plurality of band-shaped reflective parts disposed parallel to each another, and which are disposed facing each other such that the respective band-shaped reflective parts cross each other. The display unit is disposed at a position equal in height to the position of the light-controlling panel, and is constituted by a liquid crystal display, for example, and the display unit may be either a flat or three-dimensional object. The mirror member is disposed parallel to the light-controlling panel with a space there between.
Image light from the display unit is reflected by the mirror member to be then incident on the light-controlling panel, where the image light is reflected by the first and second light-controlling members and is directed into the air on a side opposite to the light entrance side (the side where the mirror member is disposed). Thereby, a real image of the image displayed on the display unit is formed in the air. By using the mirror member to bend the optical path of the image light traveling from the display unit to the light-controlling panel, the space on the light entrance side with respect to the light-controlling panel is reduced, and thereby the device is made compact and thin.